Mercurial > hg > truffle
view graal/com.oracle.graal.java/src/com/oracle/graal/java/BciBlockMapping.java @ 5678:2f714239cc68
Fix warning,
Fix to FullUnrolling
Fix to peeling when a loop end disappears
author | Gilles Duboscq <duboscq@ssw.jku.at> |
---|---|
date | Thu, 21 Jun 2012 17:27:58 +0200 |
parents | fdf19fa15ce4 |
children | 764db9ada24f |
line wrap: on
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/* * Copyright (c) 2009, 2011, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package com.oracle.graal.java; import static com.oracle.graal.bytecode.Bytecodes.*; import java.util.*; import com.oracle.graal.api.code.*; import com.oracle.graal.api.meta.*; import com.oracle.graal.bytecode.*; import com.oracle.graal.compiler.*; import com.oracle.graal.debug.*; import com.oracle.graal.nodes.*; /** * Builds a mapping between bytecodes and basic blocks and builds a conservative control flow graph (CFG). * It makes one linear passes over the bytecodes to build the CFG where it detects block headers and connects them. * <br> * It also creates exception dispatch blocks for exception handling. These blocks are between a bytecode that might * throw an exception, and the actual exception handler entries, and are later used to create the type checks with the * exception handler catch types. If a bytecode is covered by an exception handler, this bytecode ends the basic block. * This guarantees that a) control flow cannot be transferred to an exception dispatch block in the middle of a block, and * b) that every block has at most one exception dispatch block (which is always the last entry in the successor list). * <br> * If a bytecode is covered by multiple exception handlers, a chain of exception dispatch blocks is created so that * multiple exception handler types can be checked. The chains are re-used if multiple bytecodes are covered by the same * exception handlers. * <br> * Note that exception unwinds, i.e., bytecodes that can throw an exception but the exception is not handled in this method, * do not end a basic block. Not modeling the exception unwind block reduces the complexity of the CFG, and there is no * algorithm yet where the exception unwind block would matter. * <br> * The class also handles subroutines (jsr and ret bytecodes): subroutines are inlined by duplicating the subroutine blocks. * This is limited to simple, structured subroutines with a maximum subroutine nesting of 4. Otherwise, a bailout is thrown. * <br> * Loops in the methods are detected. If a method contains an irreducible loop (a loop with more than one entry), a bailout is * thrown. This simplifies the compiler later on since only structured loops need to be supported. * <br> * A data flow analysis computes the live local variables from the point of view of the interpreter. The result is used later * to prune frame states, i.e., remove local variable entries that are guaranteed to be never used again (even in the case of * deoptimization). * <br> * The algorithms and analysis in this class are conservative and do not use any assumptions or profiling information. */ public final class BciBlockMapping { public static class Block implements Cloneable { public int startBci; public int endBci; public boolean isExceptionEntry; public boolean isLoopHeader; public int loopId; public int blockID; public FixedWithNextNode firstInstruction; public FrameStateBuilder entryState; public ArrayList<Block> successors = new ArrayList<>(2); public long exits; private boolean visited; private boolean active; public long loops; public HashMap<JsrScope, Block> jsrAlternatives; public JsrScope jsrScope = JsrScope.EMPTY_SCOPE; public Block jsrSuccessor; public int jsrReturnBci; public Block retSuccessor; public boolean endsWithRet = false; public BitSet localsLiveIn; public BitSet localsLiveOut; private BitSet localsLiveGen; private BitSet localsLiveKill; public Block exceptionDispatchBlock() { if (successors.size() > 0 && successors.get(successors.size() - 1) instanceof ExceptionDispatchBlock) { return successors.get(successors.size() - 1); } return null; } public int numNormalSuccessors() { if (exceptionDispatchBlock() != null) { return successors.size() - 1; } return successors.size(); } public Block copy() { try { Block block = (Block) super.clone(); block.successors = new ArrayList<>(successors); return block; } catch (CloneNotSupportedException e) { throw new RuntimeException(e); } } @Override public String toString() { StringBuilder sb = new StringBuilder("B").append(blockID); sb.append('[').append(startBci).append("->").append(endBci); if (isLoopHeader || isExceptionEntry) { sb.append(' '); if (isLoopHeader) { sb.append('L'); } if (isExceptionEntry) { sb.append('!'); } } sb.append(']'); return sb.toString(); } } public static class ExceptionDispatchBlock extends Block { private HashMap<ExceptionHandler, ExceptionDispatchBlock> exceptionDispatch = new HashMap<>(); public ExceptionHandler handler; public int deoptBci; } /** * The blocks found in this method, in reverse postorder. */ public final List<Block> blocks; public final ResolvedJavaMethod method; public boolean hasJsrBytecodes; public Block startBlock; private final BytecodeStream stream; private final ExceptionHandler[] exceptionHandlers; private Block[] blockMap; public Block[] loopHeaders; /** * Creates a new BlockMap instance from bytecode of the given method . * @param method the compiler interface method containing the code */ public BciBlockMapping(ResolvedJavaMethod method) { this.method = method; exceptionHandlers = method.exceptionHandlers(); stream = new BytecodeStream(method.code()); this.blockMap = new Block[method.codeSize()]; this.blocks = new ArrayList<>(); this.loopHeaders = new Block[64]; } /** * Builds the block map and conservative CFG and numbers blocks. */ public void build() { makeExceptionEntries(); iterateOverBytecodes(); if (hasJsrBytecodes) { if (!GraalOptions.SupportJsrBytecodes) { throw new JsrNotSupportedBailout("jsr/ret parsing disabled"); } createJsrAlternatives(blockMap[0]); } if (Debug.isLogEnabled()) { this.log("Before BlockOrder"); } computeBlockOrder(); fixLoopBits(); initializeBlockIds(); startBlock = blockMap[0]; assert verify(); // Discard big arrays so that they can be GCed blockMap = null; if (Debug.isLogEnabled()) { this.log("Before LivenessAnalysis"); } if (GraalOptions.OptLivenessAnalysis) { Debug.scope("LivenessAnalysis", new Runnable() { @Override public void run() { computeLiveness(); } }); } } private boolean verify() { for (Block block : blocks) { assert blocks.get(block.blockID) == block; for (int i = 0; i < block.successors.size(); i++) { Block sux = block.successors.get(i); if (sux instanceof ExceptionDispatchBlock) { assert i == block.successors.size() - 1 : "Only one exception handler allowed, and it must be last in successors list"; } } } return true; } private void initializeBlockIds() { for (int i = 0; i < blocks.size(); i++) { blocks.get(i).blockID = i; } } private void makeExceptionEntries() { // start basic blocks at all exception handler blocks and mark them as exception entries for (ExceptionHandler h : this.exceptionHandlers) { Block xhandler = makeBlock(h.handlerBCI()); xhandler.isExceptionEntry = true; } } private void iterateOverBytecodes() { // iterate over the bytecodes top to bottom. // mark the entrypoints of basic blocks and build lists of successors for // all bytecodes that end basic blocks (i.e. goto, ifs, switches, throw, jsr, returns, ret) Block current = null; stream.setBCI(0); while (stream.currentBC() != Bytecodes.END) { int bci = stream.currentBCI(); if (current == null || blockMap[bci] != null) { Block b = makeBlock(bci); if (current != null) { addSuccessor(current.endBci, b); } current = b; } blockMap[bci] = current; current.endBci = bci; switch (stream.currentBC()) { case IRETURN: // fall through case LRETURN: // fall through case FRETURN: // fall through case DRETURN: // fall through case ARETURN: // fall through case RETURN: { current = null; break; } case ATHROW: { current = null; ExceptionDispatchBlock handler = handleExceptions(bci); if (handler != null) { addSuccessor(bci, handler); } break; } case IFEQ: // fall through case IFNE: // fall through case IFLT: // fall through case IFGE: // fall through case IFGT: // fall through case IFLE: // fall through case IF_ICMPEQ: // fall through case IF_ICMPNE: // fall through case IF_ICMPLT: // fall through case IF_ICMPGE: // fall through case IF_ICMPGT: // fall through case IF_ICMPLE: // fall through case IF_ACMPEQ: // fall through case IF_ACMPNE: // fall through case IFNULL: // fall through case IFNONNULL: { current = null; addSuccessor(bci, makeBlock(stream.readBranchDest())); addSuccessor(bci, makeBlock(stream.nextBCI())); break; } case GOTO: case GOTO_W: { current = null; addSuccessor(bci, makeBlock(stream.readBranchDest())); break; } case TABLESWITCH: { current = null; addSwitchSuccessors(bci, new BytecodeTableSwitch(stream, bci)); break; } case LOOKUPSWITCH: { current = null; addSwitchSuccessors(bci, new BytecodeLookupSwitch(stream, bci)); break; } case JSR: case JSR_W: { hasJsrBytecodes = true; int target = stream.readBranchDest(); if (target == 0) { throw new JsrNotSupportedBailout("jsr target bci 0 not allowed"); } Block b1 = makeBlock(target); current.jsrSuccessor = b1; current.jsrReturnBci = stream.nextBCI(); current = null; addSuccessor(bci, b1); break; } case RET: { current.endsWithRet = true; current = null; break; } case INVOKEINTERFACE: case INVOKESPECIAL: case INVOKESTATIC: case INVOKEVIRTUAL: { current = null; addSuccessor(bci, makeBlock(stream.nextBCI())); ExceptionDispatchBlock handler = handleExceptions(bci); if (handler != null) { addSuccessor(bci, handler); } break; } case IASTORE: case LASTORE: case FASTORE: case DASTORE: case AASTORE: case BASTORE: case CASTORE: case SASTORE: case IALOAD: case LALOAD: case FALOAD: case DALOAD: case AALOAD: case BALOAD: case CALOAD: case SALOAD: case PUTFIELD: case GETFIELD: { ExceptionDispatchBlock handler = handleExceptions(bci); if (handler != null) { current = null; addSuccessor(bci, makeBlock(stream.nextBCI())); addSuccessor(bci, handler); } } } stream.next(); } } private Block makeBlock(int startBci) { Block oldBlock = blockMap[startBci]; if (oldBlock == null) { Block newBlock = new Block(); newBlock.startBci = startBci; blockMap[startBci] = newBlock; return newBlock; } else if (oldBlock.startBci != startBci) { // Backward branch into the middle of an already processed block. // Add the correct fall-through successor. Block newBlock = new Block(); newBlock.startBci = startBci; newBlock.endBci = oldBlock.endBci; newBlock.successors.addAll(oldBlock.successors); oldBlock.endBci = startBci - 1; oldBlock.successors.clear(); oldBlock.successors.add(newBlock); for (int i = startBci; i <= newBlock.endBci; i++) { blockMap[i] = newBlock; } return newBlock; } else { return oldBlock; } } private void addSwitchSuccessors(int predBci, BytecodeSwitch bswitch) { for (int i = 0; i < bswitch.numberOfCases(); i++) { addSuccessor(predBci, makeBlock(bswitch.targetAt(i))); } addSuccessor(predBci, makeBlock(bswitch.defaultTarget())); } private void addSuccessor(int predBci, Block sux) { Block predecessor = blockMap[predBci]; if (sux.isExceptionEntry) { throw new BailoutException("Exception handler can be reached by both normal and exceptional control flow"); } predecessor.successors.add(sux); } private final HashSet<Block> jsrVisited = new HashSet<>(); private void createJsrAlternatives(Block block) { jsrVisited.add(block); JsrScope scope = block.jsrScope; if (block.endsWithRet) { block.retSuccessor = blockMap[scope.nextReturnAddress()]; block.successors.add(block.retSuccessor); assert block.retSuccessor != block.jsrSuccessor; } Debug.log("JSR alternatives block %s sux %s jsrSux %s retSux %s jsrScope %s", block, block.successors, block.jsrSuccessor, block.retSuccessor, block.jsrScope); if (block.jsrSuccessor != null || !scope.isEmpty()) { for (int i = 0; i < block.successors.size(); i++) { Block successor = block.successors.get(i); JsrScope nextScope = scope; if (successor == block.jsrSuccessor) { nextScope = scope.push(block.jsrReturnBci); } if (successor == block.retSuccessor) { nextScope = scope.pop(); } if (!successor.jsrScope.isPrefixOf(nextScope)) { throw new JsrNotSupportedBailout("unstructured control flow (" + successor.jsrScope + " " + nextScope + ")"); } if (!nextScope.isEmpty()) { Block clone; if (successor.jsrAlternatives != null && successor.jsrAlternatives.containsKey(nextScope)) { clone = successor.jsrAlternatives.get(nextScope); } else { if (successor.jsrAlternatives == null) { successor.jsrAlternatives = new HashMap<>(); } clone = successor.copy(); clone.jsrScope = nextScope; successor.jsrAlternatives.put(nextScope, clone); } block.successors.set(i, clone); if (successor == block.jsrSuccessor) { block.jsrSuccessor = clone; } if (successor == block.retSuccessor) { block.retSuccessor = clone; } } } } for (Block successor : block.successors) { if (!jsrVisited.contains(successor)) { createJsrAlternatives(successor); } } } private HashMap<ExceptionHandler, ExceptionDispatchBlock> initialExceptionDispatch = new HashMap<>(); private ExceptionDispatchBlock handleExceptions(int bci) { ExceptionDispatchBlock lastHandler = null; for (int i = exceptionHandlers.length - 1; i >= 0; i--) { ExceptionHandler h = exceptionHandlers[i]; if (h.startBCI() <= bci && bci < h.endBCI()) { if (h.isCatchAll()) { // Discard all information about succeeding exception handlers, since they can never be reached. lastHandler = null; } HashMap<ExceptionHandler, ExceptionDispatchBlock> exceptionDispatch = lastHandler != null ? lastHandler.exceptionDispatch : initialExceptionDispatch; ExceptionDispatchBlock curHandler = exceptionDispatch.get(h); if (curHandler == null) { curHandler = new ExceptionDispatchBlock(); curHandler.startBci = -1; curHandler.endBci = -1; curHandler.deoptBci = bci; curHandler.handler = h; curHandler.successors.add(blockMap[h.handlerBCI()]); if (lastHandler != null) { curHandler.successors.add(lastHandler); } exceptionDispatch.put(h, curHandler); } lastHandler = curHandler; } } return lastHandler; } private boolean loopChanges; private void fixLoopBits() { do { loopChanges = false; for (Block b : blocks) { b.visited = false; } long loop = fixLoopBits(blockMap[0]); if (loop != 0) { // There is a path from a loop end to the method entry that does not pass the loop header. // Therefore, the loop is non reducible (has more than one entry). // We don't want to compile such methods because the IR only supports structured loops. throw new BailoutException("Non-reducible loop"); } } while (loopChanges); } private void computeBlockOrder() { long loop = computeBlockOrder(blockMap[0]); if (loop != 0) { // There is a path from a loop end to the method entry that does not pass the loop header. // Therefore, the loop is non reducible (has more than one entry). // We don't want to compile such methods because the IR only supports structured loops. throw new BailoutException("Non-reducible loop"); } // Convert postorder to the desired reverse postorder. Collections.reverse(blocks); } public void log(String name) { if (Debug.isLogEnabled()) { String n = System.lineSeparator(); StringBuilder sb = new StringBuilder(Debug.currentScope()).append("BlockMap ").append(name).append(" :"); sb.append(n); Iterable<Block> it; if (blocks.isEmpty()) { it = new HashSet<>(Arrays.asList(blockMap)); } else { it = blocks; } for (Block b : it) { if (b == null) { continue; } sb.append("B").append(b.blockID).append(" (").append(b.startBci).append(" -> ").append(b.endBci).append(")"); if (b.isLoopHeader) { sb.append(" LoopHeader"); } if (b.isExceptionEntry) { sb.append(" ExceptionEntry"); } sb.append(n).append(" Sux : "); for (Block s : b.successors) { sb.append("B").append(s.blockID).append(" (").append(s.startBci).append(" -> ").append(s.endBci).append(")"); if (s.isExceptionEntry) { sb.append("!"); } sb.append(" "); } sb.append(n).append(" Loop : "); long l = b.loops; int pos = 0; while (l != 0) { int lMask = 1 << pos; if ((l & lMask) != 0) { sb.append("B").append(loopHeaders[pos].blockID).append(" "); l &= ~lMask; } pos++; } sb.append(n).append(" Exits : "); l = b.exits; pos = 0; while (l != 0) { int lMask = 1 << pos; if ((l & lMask) != 0) { sb.append("B").append(loopHeaders[pos].blockID).append(" "); l &= ~lMask; } pos++; } sb.append(n); } Debug.log(sb.toString()); } } /** * The next available loop number. */ private int nextLoop; /** * Mark the block as a loop header, using the next available loop number. * Also checks for corner cases that we don't want to compile. */ private void makeLoopHeader(Block block) { if (!block.isLoopHeader) { block.isLoopHeader = true; if (block.isExceptionEntry) { // Loops that are implicitly formed by an exception handler lead to all sorts of corner cases. // Don't compile such methods for now, until we see a concrete case that allows checking for correctness. throw new BailoutException("Loop formed by an exception handler"); } if (nextLoop >= Long.SIZE) { // This restriction can be removed by using a fall-back to a BitSet in case we have more than 64 loops // Don't compile such methods for now, until we see a concrete case that allows checking for correctness. throw new BailoutException("Too many loops in method"); } assert block.loops == 0; block.loops = (long) 1 << (long) nextLoop; Debug.log("makeLoopHeader(%s) -> %x", block, block.loops); loopHeaders[nextLoop] = block; block.loopId = nextLoop; nextLoop++; } assert Long.bitCount(block.loops) == 1; } /** * Depth-first traversal of the control flow graph. The flag {@linkplain Block#visited} is used to * visit every block only once. The flag {@linkplain Block#active} is used to detect cycles (backward * edges). */ private long computeBlockOrder(Block block) { if (block.visited) { if (block.active) { // Reached block via backward branch. makeLoopHeader(block); // Return cached loop information for this block. return block.loops; } else if (block.isLoopHeader) { return block.loops & ~(1L << block.loopId); } else { return block.loops; } } block.visited = true; block.active = true; int loops = 0; for (Block successor : block.successors) { // Recursively process successors. loops |= computeBlockOrder(successor); } block.loops = loops; Debug.log("computeBlockOrder(%s) -> %x", block, block.loops); if (block.isLoopHeader) { loops &= ~(1L << block.loopId); } block.active = false; blocks.add(block); return loops; } private long fixLoopBits(Block block) { if (block.visited) { // Return cached loop information for this block. if (block.isLoopHeader) { return block.loops & ~(1L << block.loopId); } else { return block.loops; } } block.visited = true; long loops = block.loops; for (Block successor : block.successors) { // Recursively process successors. loops |= fixLoopBits(successor); } for (Block successor : block.successors) { successor.exits = loops & ~successor.loops; } if (block.loops != loops) { loopChanges = true; block.loops = loops; Debug.log("fixLoopBits0(%s) -> %x", block, block.loops); } if (block.isLoopHeader) { loops &= ~(1L << block.loopId); } return loops; } private void computeLiveness() { for (Block block : blocks) { computeLocalLiveness(block); } boolean changed; int iteration = 0; do { Debug.log("Iteration %d", iteration); changed = false; for (int i = blocks.size() - 1; i >= 0; i--) { Block block = blocks.get(i); Debug.log(" start B%d [%d, %d] in: %s out: %s gen: %s kill: %s", block.blockID, block.startBci, block.endBci, block.localsLiveIn, block.localsLiveOut, block.localsLiveGen, block.localsLiveKill); boolean blockChanged = (iteration == 0); if (block.successors.size() > 0) { int oldCardinality = block.localsLiveOut.cardinality(); for (Block sux : block.successors) { Debug.log(" Successor B%d: %s", sux.blockID, sux.localsLiveIn); block.localsLiveOut.or(sux.localsLiveIn); } blockChanged |= (oldCardinality != block.localsLiveOut.cardinality()); } if (blockChanged) { block.localsLiveIn.clear(); block.localsLiveIn.or(block.localsLiveOut); block.localsLiveIn.xor(block.localsLiveKill); block.localsLiveIn.or(block.localsLiveGen); Debug.log(" end B%d [%d, %d] in: %s out: %s gen: %s kill: %s", block.blockID, block.startBci, block.endBci, block.localsLiveIn, block.localsLiveOut, block.localsLiveGen, block.localsLiveKill); } changed |= blockChanged; } iteration++; } while (changed); } private void computeLocalLiveness(Block block) { block.localsLiveIn = new BitSet(method.maxLocals()); block.localsLiveOut = new BitSet(method.maxLocals()); block.localsLiveGen = new BitSet(method.maxLocals()); block.localsLiveKill = new BitSet(method.maxLocals()); if (block.startBci < 0 || block.endBci < 0) { return; } stream.setBCI(block.startBci); while (stream.currentBCI() <= block.endBci) { switch (stream.currentBC()) { case RETURN: if (method.isConstructor() && method.holder().superType() == null) { // return from Object.init implicitly registers a finalizer // for the receiver if needed, so keep it alive. loadOne(block, 0); } break; case LLOAD: case DLOAD: loadTwo(block, stream.readLocalIndex()); break; case LLOAD_0: case DLOAD_0: loadTwo(block, 0); break; case LLOAD_1: case DLOAD_1: loadTwo(block, 1); break; case LLOAD_2: case DLOAD_2: loadTwo(block, 2); break; case LLOAD_3: case DLOAD_3: loadTwo(block, 3); break; case ILOAD: case IINC: case FLOAD: case ALOAD: case RET: loadOne(block, stream.readLocalIndex()); break; case ILOAD_0: case FLOAD_0: case ALOAD_0: loadOne(block, 0); break; case ILOAD_1: case FLOAD_1: case ALOAD_1: loadOne(block, 1); break; case ILOAD_2: case FLOAD_2: case ALOAD_2: loadOne(block, 2); break; case ILOAD_3: case FLOAD_3: case ALOAD_3: loadOne(block, 3); break; case LSTORE: case DSTORE: storeTwo(block, stream.readLocalIndex()); break; case LSTORE_0: case DSTORE_0: storeTwo(block, 0); break; case LSTORE_1: case DSTORE_1: storeTwo(block, 1); break; case LSTORE_2: case DSTORE_2: storeTwo(block, 2); break; case LSTORE_3: case DSTORE_3: storeTwo(block, 3); break; case ISTORE: case FSTORE: case ASTORE: storeOne(block, stream.readLocalIndex()); break; case ISTORE_0: case FSTORE_0: case ASTORE_0: storeOne(block, 0); break; case ISTORE_1: case FSTORE_1: case ASTORE_1: storeOne(block, 1); break; case ISTORE_2: case FSTORE_2: case ASTORE_2: storeOne(block, 2); break; case ISTORE_3: case FSTORE_3: case ASTORE_3: storeOne(block, 3); break; } stream.next(); } } private static void loadTwo(Block block, int local) { loadOne(block, local); loadOne(block, local + 1); } private static void loadOne(Block block, int local) { if (!block.localsLiveKill.get(local)) { block.localsLiveGen.set(local); } } private static void storeTwo(Block block, int local) { storeOne(block, local); storeOne(block, local + 1); } private static void storeOne(Block block, int local) { if (!block.localsLiveGen.get(local)) { block.localsLiveKill.set(local); } } }